The present invention relates to an indexable cutting insert for chip removal during machining.
Presently, cutting inserts of hard and wear resistant materials are used in tools for chip removal during machining. The geometry of some of these cutting inserts is such as to minimize power requirements for metal cutting operations. At the same time, the geometry of the cutting insert is required to allow chip breaking under a wide range of parameters, for example depth of cut or feed speed. Several cutting inserts comprise upper face protrusions adapted to facilitate the development and breaking of chips. These well-known designs of the cutting inserts however require usage of high cutting power to overcome higher frictional force arising at protrusions on the upper face.
A cutting insert disclosed in U.S. Pat. No. 3,815,192 comprises several protrusions of circular basic shape along the perimeter of the upper face defining zones of chip formation among them. According to U.S. Pat. No. 3,973,308, several notches are formed on the upper face of the cutting insert to allow chips to slip by without substantial deformation.
In the design according to EP-A2-332 085, the cutting insert has the shape of a polygonal body and comprises opposed upper and lower faces and a peripheral wall therebetween. The cutting edge is formed at the intersection of the upper face and a peripheral wall. The cutting insert has several spatial protrusions in the shape of oblong ribs on the upper and lower faces, which ribs serve to break the chip. In the solution according to EP 577 573, the cutting insert corner has spaced protrusions symmetrically organized relative to the bisector of cutting corner.
Further known is the cutting insert according to U.S. Pat. No. 4,741,649, where chip breaking is done by several protrusions, which are connected with a mid portion of the upper face and have a truncated spherical shape and which differ in size such that smaller protrusions are located close to the cutting corners, where the width is narrower. At chip breaking with this cutting insert, the chip has undesirably large contact with the spherical area of the protrusion and with a concave rear face, which causes higher frictional forces and thereby increases cutting forces and heat dissipation, such that heat transfers into cutting insert. A similar solution can be seen in U.S. Pat. No. 4,597,696.
In the design according to EP-A1-567 899, the cutting insert corner has a bean-shaped protrusion split by a narrow groove in the direction of the bisector of the insert corner. One disadvantage of this known solution is decreased protection of the cutting corner since abrasion of the protrusion arises due to friction from chips and deformation and directional change of chip direction during the cutting process caused by the narrow groove, which decreases durability of the cutting insert.